Computer Aided Design (CAD) software tools are commonly used to prepare a CAD model or models representing a structure, such as a building. A CAD model can incorporate a physical model, i.e., representations of physical elements, such as columns, beams, slabs, walls, and the like that will be included in the structure. Drawings prepared from such a model can be used in the actual physical construction of the corresponding structure. The CAD model may be prepared and edited by various individuals, including architects and structural engineers. As part of a design stage, a structural analysis is typically performed on elements that will be included in the structure, for example, to ensure that there is sufficient load bearing capacity.
Structural analysis software is available to perform analysis of a CAD model. Conventional structural analysis software receives as input an analytical representation of a physical structure. An analytical representation is typically different than a representation of the physical elements, e.g., columns, beams, etc. It is an idealized mathematical model that may represent only a portion of a structure such as one floor of a building. For example, an analytical representation may be a wire frame representation of the physical elements, and the wire frame elements can include or be associated with properties (e.g., weight, moment of inertia, cross-sectional area), member connectivity and/or end conditions (e.g., pinned, free, fixed). Typically, the analytical representation is prepared separately and is used for the structural analysis and perhaps other types of analyses that are performed in the design stage.
The analytical representation can be subjected to load simulation in a structural analysis program, for example, to identify stress levels in the various physical elements. On the basis of the analysis, analytical elements in the analytical representation may be modified (e.g., resized or other properties changed) and the analytical representation reanalyzed in an iterative fashion. The results of the analysis can be used to update corresponding physical elements in the CAD model. Analytical representations can be automatically generated from a CAD model.
In the typical design of concrete floor slabs and walls there is a need to incorporate into the CAD model a large number of physical reinforcement elements such as steel bars (“rebar”) which serve to strengthen the concrete. However, the process of manually creating each reinforcement element in a CAD tool can be tedious and error prone. Additionally, changes in geometry of slabs or walls may require a labor intensive reconfiguration of the reinforcement elements. Some CAD tools represent reinforcement elements as fully modeled three-dimensional (3D) physical elements. While this allows for accurate renderings in plan and cut sections, much of the layout and editing of reinforcement elements is typically done manually. Moreover, because of the complexity of 3D models, there is tremendous overhead in manipulating CAD models with even a modest number of reinforcement objects.